Automatic and semiautomatic rifles, including firearms based on the AR-15 service rifle and similar platforms, use impingement mechanisms to automatically reload. Capturing energy from fired ammunition to reload is typically accomplished using either direct impingement, i.e., porting pressurized gas from the barrel through a gas key to act directly on a bolt carrier, or using a piston system, in which gas drives a piston that impinges on an integral key on the bolt carrier. Both of these systems cause a piston-like action of the bolt carrier in the rifle's upper receiver, and in either case, repeated travel of the bolt carrier within the upper receiver coordinates cycling of the action which is inclusive of unlocking the bolt, ejecting the spent cartridge, chambering a new round, and so forth.
Ensuring a continuous and reliable automatic reloading operation during rapid firing over time requires that the bolt carrier travel smoothly in the upper receiver. Bolt carriers and upper receivers presently known in the art rely principally on precision milling or machining to produce a fit that adequately constrains the bolt carrier while providing adequate freedom of the back-and-forth movement. Despite a substantially complimentary fit, both the bolt carrier and upper receiver eventually suffer damage caused by sliding contact over prolonged periods of repeated firing. Heat buildup caused by friction is also a concern.
Direct impingement mechanisms are increasing disfavored due to a tendency to cause gas fouling. Over time, as carbon-laden gasses travel through the bolt carrier, the risk of a malfunction increases. Because automatic and semiautomatic rifles are often built on a common platform customarily employing standardized interchangeable parts, and due to the increasing preference for piston driven systems, users frequently customize firearms with newly developed aftermarket alternative components. These modifications occasionally result in a slightly imprecise fit between the bolt carrier and upper receiver, compounding existing friction-related problems and accelerating damage to the reloading mechanism.
Other components within firearms that perform repeated sliding movement and rely on precise machining include but are not limited to shotgun shell followers. As is known in the art, shotgun shell followers are operably coupled to a spring in the magazine tube of a shotgun and are operable to slidably move within the magazine tube and engage the shotgun shell adjacent thereto during the loading and firing process. The movement of the shotgun shell follower impacts performance of the firearm during the loading and firing process.
Due to the problems in the art, there is a need for improved firearm components such as but not limited to a bolt carrier and shotgun shell follower that avoids excessive friction from sliding movement during use of the firearm. There is also a need for a bolt carrier and shotgun shell follower capable of assembly as part of customizing or retrofitting a firearm. Additionally, it is desired for a bolt carrier and shotgun shell follower that are formed from a single piece of material, making it simple and inexpensive to mass produce.